WASHINGTON — The Obama administration is preparing financial sanctions that could be imposed on Ukrainian officials and protest leaders if violence escalates in the political crisis gripping Ukraine, congressional aides said on Wednesday.

Congressional aides, who asked not to be identified by name because of the sensitive subject, said they had discussed the sanction preparations with administration officials.

They said final details of the package have not been worked out, but it could be put in place quickly against government officials — or leaders of the protest movement — in case of widespread violence.

Six people have been killed in Kiev and other Ukrainian cities in protests that erupted more than two months ago after President Viktor Yanukovich walked away from a treaty with the European Union under pressure from Russia.

Alarmed by the crisis, Washington has revoked the visas of some Ukrainian officials.

President Barack Obama referred to Ukraine in his State of the Union address on Tuesday, voicing support for the principle that all people have the right to free expression.

Vice President Joe Biden has spoken to Yanukovich at least three times. And two U.S. senators, Republican John McCain of Arizona and Democrat Chris Murphy of Connecticut, traveled to Kiev last month and addressed demonstrations.

The House Foreign Affairs Committee on Wednesday passed a resolution calling on all sides in the confrontation to refrain from violence and work toward a peaceful resolution.

"The situation in Ukraine remains very volatile and more needs to be done," said Representative Eliot Engel, the New York Democrat who sponsored the resolution. "We must remain engaged."

However, U.S. lawmakers and Obama administration officials said they were encouraged by recent developments, including the Ukrainian parliament's vote to repeal anti-protest laws.

"We were encouraged that Ukraine's parliament repealed the most egregious of the most anti-democratic laws. Today we want to urge President Yanukovich to sign the repeal laws," State Department spokeswoman Jen Psaki said at a news briefing.

She told reporters the State Department has been willing to consider sanctions but no decision has been made.

Alarm has grown elsewhere in the West. German Chancellor Angela Merkel telephoned Russian President Vladimir Putin and Yanukovich on Wednesday, urging a constructive dialogue between the government and opposition.

Putin raised the pressure on Ukraine on Wednesday, saying Russia would wait until Ukraine forms a new government before fully implementing a $15 billion bailout deal that Kiev urgently needs.

The Obama administration is preparing financial sanctions that could be imposed on Ukrainian officials and protest leaders if violence escalates in the political crisis gripping Ukraine, congressional aides said on Wednesday.